The invention relates to a method for joining at least two parts to be joined that are arranged so as to overlap at least in a joining zone using a joining element according to the preamble of claim 1.
From DE 103 29 447 A1 a joining method for joining parts that are to be joined and are arranged so as to overlap each other is known which uses a joining element having a shaft region that is free of undercuts. In this disclosed joining method material of a first joining part is urged during the joining process through a punch recess of the second joining part, which recess is generated during the joining method, wherein an undesired punch piece is generated. After urging material of the first joining part through the generated punch opening of the second joining part the material of the first joining part is compressed relative to the second joining part so that a form fit is generated is between the first and second joining part. A disadvantage of this method is that an undesired slug is generated that has to be reliably removed from the joining site. In addition uncoated border regions are generated when urging the first material through the just generated punch opening in the second joining part, which may lead to undesired corrosion.
In DE 10 2011 009 649 A1 the method generally known as solid punch riveting is disclosed. In such a method the used joining element has at least in the shaft region undercuts or grooves and indentations that extend in circumferential direction and into which material is pressed with a die so as to ensure that the solid rivet is form-fittingly seated in the material of the two joining parts.
A disadvantage of such a so-called solid punch riveting is that at least one, or even two slugs of the two joining parts are generated. In particular when the joining parts are made of different materials, two slugs are particularly disadvantageous because after joining with the solid rivet they have to be separated again according to material to be recycled.
From DE 10 2008 005 289 a fastening arrangement of a superstructure component, in particular of a roof element for a vehicle roof on a body of a motor vehicle, is known. In this fastening arrangement joining or fastening is accomplished by the solid punch riveting process, in which two slugs are generated during introduction of the solid rivet into the components to be joined. A disadvantage in this method is that slugs are produced, which involves increased disposal costs.
It is an object of the invention to avoid the disadvantages of the state of the art. It is another object of the invention to provide a joining method which uses a joining element and which minimizes corrosion sensitivity in the region of the joining sites.
A further object of the invention is to provide a joining method in which no free slugs are produced that have to be disposed.
A further object of the invention is to provide a joining method with a simple formed joining element, which has sufficient removal strengths or removal forces.